Cardiac cell repair therapy: a clinical perspective

The Myocardial Microenvironment Modulates the Biology of Transplanted Mesenchymal Stem Cells

PURPOSE

The maximal efficacy of cell therapy depends on the survival of stem cells, as well as on the phenotypic and biologic changes that may occur on these cells after transplantation. It has been hypothesized that the post-ischemic myocardial microenvironment can play a critical role in these changes, potentially affecting the survival and reparative potential of mesenchymal stem cells (MSCs). Here, we use a dual reporter gene sensor for the in vivo monitoring of the phenotype of MSCs and study their therapeutic effect on cardiac function.

PROCEDURES

The mitochondrial sensor was tested in cell culture in response to different mitochondrial stressors. For in vivo testing, MSCs (3 × 10⁵) were delivered in a murine ischemia-reperfusion (IR) model. Bioluminescence imaging was used to assess the mitochondrial biology and the viability of transplanted MSCs, while high-resolution ultrasound provided a non-invasive analysis of cardiac contractility and dyssynchrony.

RESULTS

The mitochondrial sensor showed increased activity in response to mitochondrial stressors. Furthermore, when tested in the living subject, it showed a significant increase in mitochondrial dysfunction in MSCs delivered in IR, compared with those delivered under sham conditions. Importantly, MSCs delivered to ischemic hearts, despite their mitochondrial stress and poor survival, were able to induce a significant improvement in cardiac function, through decreased collagen deposition and resynchronization/contractility of left ventricular wall motion.

CONCLUSIONS

The ischemic myocardium induces changes in the phenotype of transplanted MSCs. Despite their limited survival, MSCs still elicit a certain therapeutic response, as evidenced by improvement in myocardial remodeling and cardiac function. Maximization of the survival and reparative efficacy of stem cells remains a key for the success of stem cell therapies.

Selection of human induced pluripotent stem cells lines optimization of cardiomyocytes differentiation in an integrated suspension microcarrier bioreactor

Background

The production of large quantities of cardiomyocyte is essential for the needs of cellular therapies. This study describes the selection of a human-induced pluripotent cell (hiPSC) line suitable for production of cardiomyocytes in a fully integrated bioprocess of stem cell expansion and differentiation in microcarrier stirred tank reactor.

Methods

Five hiPSC lines were evaluated first for their cardiac differentiation efficiency in monolayer cultures followed by their expansion and differentiation compatibility in microcarrier (MC) cultures under continuous stirring conditions.

Results

Three cell lines were highly cardiogenic but only one (FR202) of them was successfully expanded on continuous stirring MC cultures. FR202 was thus selected for cardiac differentiation in a 22-day integrated bioprocess under continuous stirring in a stirred tank bioreactor. In summary, we integrated a MC-based hiPSC expansion (phase 1), CHIR99021-induced cardiomyocyte differentiation step (phase 2), purification using the lactate-based treatment (phase 3) and cell recovery step (phase 4) into one process in one bioreactor, under restricted oxygen control (< 30% DO) and continuous stirring with periodic batch-type media exchanges. High density of undifferentiated hiPSC (2 ± 0.4 × 10⁶ cells/mL) was achieved in the expansion phase. By controlling the stirring speed and DO levels in the bioreactor cultures, 7.36 ± 1.2 × 10⁶ cells/mL cardiomyocytes with > 80% Troponin T were generated in the CHIR99021-induced differentiation phase. By adding lactate in glucose-free purification media, the purity of cardiomyocytes was enhanced (> 90% Troponin T), with minor cell loss as indicated by the increase in sub-G1 phase and the decrease of aggregate sizes. Lastly, we found that the recovery period is important for generating purer and functional cardiomyocytes (> 96% Troponin T). Three independent runs in a 300-ml working volume confirmed the robustness of this process.

Conclusion

A streamlined and controllable platform for large quantity manufacturing of pure functional atrial, ventricular and nodal cardiomyocytes on MCs in conventional-type stirred tank bioreactors was established, which can be further scaled up and translated to a good manufacturing practice-compliant production process, to fulfill the quantity requirements of the cellular therapeutic industry.

Supplementary information

The online version of this article (10.1186/s13287-020-01618-6) contains supplementary material, which is available to authorized users.

Autologous CXCR4+ Hematopoietic Stem Cells Injected into the Scar Tissue of Chronic Myocardial Infarction Patients Normalizes Tissue Contractility and Perfusion

BACKGROUND

Chronic myocardial infarction (CMI), represents a public health and a financial burden. Since stem cell transplant is used to regenerate cardiac tissue after acute myocardial infarction.

AIM OF THE STUDY

To determine if autologous CXCR4 stem cells could restore damaged myocardial tissue in patients with CMI lesions.

METHODS

20 NYHA grade III male patients with CMI defined by clinical, biochemical, ECG and echocardiographic parameters were included. Patients were treated with G-CSF for 6 d before isolating their autologous stem cells from PBMCs. Cell phenotyping was done by cytofluorometry using monoclonal antibodies (anti-CXCR4, -CD34, -48, -117, -133, -Ki67, -SDF1 and CXCR4); CXCR4 cell subpopulations isolated by sorting were adjusted to 1 × 10⁸ cells by subpopulation and injected in a circular pattern into the cicatrix previously defined by echocardiography.

RESULTS

Patients were followed for 6 and 12 months. Six months after cell implant improvements in left ventricle ejection fraction (from 33-50%), stress rate values (from -3/-9% to -18/-22%), stress tests (from 4-12 METS), and the quantity of left ventricle affected segments (3-9) disappeared according to the G-SPECT images. 12 months evaluations did not show significant differences. Interestingly, 3 months after cell implant the ECG showed normal electrical activity in 9 patients whereas after 6 months it was normal in all the patients.

CONCLUSIONS

These results ratify that locally injected autologous CXCR4+ bone marrow-derived stem cells have a physiological and a clinical impact in patients with CMI.

Changing Metabolism in Differentiating Cardiac Progenitor Cells-Can Stem Cells Become Metabolically Flexible Cardiomyocytes?

The heart is a metabolic omnivore and the adult heart selects the substrate best suited for each circumstance, with fatty acid oxidation preferred in order to fulfill the high energy demand of the contracting myocardium. The fetal heart exists in an hypoxic environment and obtains the bulk of its energy via glycolysis. After birth, the "fetal switch" to oxidative metabolism of glucose and fatty acids has been linked to the loss of the regenerative phenotype. Various stem cell types have been used in differentiation studies, but most are cultured in high glucose media. This does not change in the majority of cardiac differentiation protocols. Despite the fact that metabolic state affects marker expression and cellular function and activity, the substrate composition is currently being overlooked. In this review we discuss changes in cardiac metabolism during development, the various protocols used to differentiate progenitor cells to cardiomyocytes, what is known about stem cell metabolism and how consideration of metabolism can contribute toward maturation of stem cell-derived cardiomyocytes.

Surface-modified polymers for cardiac tissue engineering

Cardiovascular disease (CVD), leading to myocardial infarction and heart failure, is one of the major causes of death worldwide. The physiological system cannot significantly regenerate the capabilities of a damaged heart. The current treatment involves pharmacological and surgical interventions; however, less invasive and more cost-effective approaches are sought. Such new approaches are developed to induce tissue regeneration following injury. Hence, regenerative medicine plays a key role in treating CVD. Recently, the extrinsic stimulation of cardiac regeneration has involved the use of potential polymers to stimulate stem cells toward the differentiation of cardiomyocytes as a new therapeutic intervention in cardiac tissue engineering (CTE). The therapeutic potentiality of natural or synthetic polymers and cell surface interactive factors/polymer surface modifications for cardiac repair has been demonstrated in vitro and in vivo. This review will discuss the recent advances in CTE using polymers and cell surface interactive factors that interact strongly with stem cells to trigger the molecular aspects of the differentiation or formulation of cardiomyocytes for the functional repair of heart injuries or cardiac defects.

MiR-147b inhibits cell viability and promotes apoptosis of rat H9c2 cardiomyocytes via down-regulating KLF13 expression

Recently, microRNAs (miRNAs) have been shown to involve in the process of heart failure. This study aims to investigate the functional role of miR-147b in rat H9c2 cardiomyocytes and explore the underlying molecular mechanisms. Cell viability of H9c2 cells was detected by MTT assay. Cell apoptosis was detected by flow cytometry. Expression of miR-147b and KLF13 mRNA was detected by quantitative real-time PCR. The relationship between miR-147b and KLF13 was verified by dual-luciferase reporter assay. Protein levels were detected by western blot analysis. It was found that H2O2 inhibited cell viability and promoted cell apoptosis of H9c2 cells in a concentration-dependent manner. MiR-147b overexpression suppressed cell viability and increased apoptosis in H9c2 cells, while knock-down of miR-147b increased cell viability and reduced apoptosis in H2O2-treated H9c2 cells. Luciferase reporter assay and in vitro functional assay showed that KLF13 was a downstream target of miR-147b, and KLF13 knock-down suppressed cell viability and induced apoptosis in H9c2 cells. Enforced expression of KLF13 restored the effects of miR-147b overexpression on cell viability and apoptosis in H9c2 cells. MiR-147b modulated the expression levels of apoptosis-related proteins, and the effects of miR-147b overexpression on apoptosis-related proteins levels were prevented by enforced expression of KLF13 in H9c2 cells. The in vivo experiments showed that miR-147b was up-regulated, and KLF13 was down-regulated in the myocardial tissues from rats with chronic heart failure. Collectively, miR-147b inhibits viability and promotes cell apoptosis by targeting KLF13 in H9c2 cells, which may be associated with the pathogenesis of heart failure.

[Stem cells: searching predisposition to cardiac commitment by surface markers expression]

It is well-known that cardiovascular diseases are the leading cause of death worldwide, and represent an important economic burden to health systems. In an attempt to solve this problem, stem cell therapy has emerged as a therapeutic option. Within the last 20 years, a great variety of stem cells have been used in different myocardial infarction models. Up until now, the use of cardiac stem cells (CSCs) has seemed to be the best option, but the inaccessibility and scarcity of these cells make their use unreliable. Additionally, there is a high risk as they have to be obtained directly from the heart of the patient. Unlike CSCs, adult stem cells originating from bone marrow or adipose tissue, among others, appear to be an attractive option due to their easier accessibility and abundance, but particularly due to the probable existence of cardiac progenitors among their different sub-populations. In this review an analysis is made of the surface markers present in CSCs compared with other adult stem cells. This suggested the pre-existence of cells sharing specific surface markers with CSCs, a predictable immunophenotype present in some cells, although in low proportions, and with a potential of cardiac differentiation that could be similar to CSCs, thus increasing their therapeutic value. This study highlights new perspectives regarding MSCs that would enable some of these sub-populations to be differentiated at cardiac tissue level.

Regenerating Heart Using a Novel Compound and Human Wharton Jelly Mesenchymal Stem Cells

BACKGROUND

Myocardial infarction is a major problem in health system and most conventional therapy is not led to restoration of the health. Stem cell therapy is a method to regenerate the heart but today appropriate cell source and scaffold selection as extracellular matrix to achieve the best effect is disputing.

AIM OF THE STUDY

In this study a combination of human Wharton jelly mesenchymal stem cells (HWJMSCs) with a novel compound consisting polyethylene glycol (PEG), hyaluronic acid and chitosan is presented to heart regeneration.

METHODS

After proliferation and expansion of HWJMSCs, these cells were mixed with scaffold and injected into the infarcted rabbit myocardium. After two months cardiac function and infarcted area were evaluated. Immunohistochemistry performed for vessel count and demonstrating of differentiation ability into cardiomyocytes. To confirm this ability PCR was done. Scanning electron microscope was used to evaluate angiogenesis.

RESULTS

Improving cardiac function was higher in cell/scaffold group than the others and it was confirmed by SPECT results which showed least defect size in the myocardium. There were a lot of neoangiogenesis in the target group and also cardiomyogenesis observed in cell/scaffold group. PCR results confirmed the presence of differentiated cardiomyocytes and SEM showed well developed vessel in this group.

CONCLUSIONS

Comparing macroscopic and microscopic results between all groups revealed that HWJMSC in combination with this scaffold led to brilliant results regarding cardiac function, angiogenesis and cardiogenesis. It is recommended using these cells and materials for cardiac tissue engineering and regeneration therapy.

Tuning of major signaling networks (TGF-β, Wnt, Notch and Hedgehog) by miRNAs in human stem cells commitment to different lineages: Possible clinical application

Two distinguishing characteristics of stem cells, their continuous division in the undifferentiated state and growth into any cell types, are orchestrated by a number of cell signaling pathways. These pathways act as a niche factor in controlling variety of stem cells. The core stem cell signaling pathways include Wingless-type (Wnt), Hedgehog (HH), and Notch. Additionally, they critically regulate the self-renewal and survival of cancer stem cells. Conversely, stem cells' main properties, lineage commitment and stemness, are tightly controlled by epigenetic mechanisms such as DNA methylation, histone modifications and non-coding RNA-mediated regulatory events. MicroRNAs (miRNAs) are cellular switches that modulate stem cells outcomes in response to diverse extracellular signals. Numerous scientific evidences implicating miRNAs in major signal transduction pathways highlight new crosstalks of cellular processes. Aberrant signaling pathways and miRNAs levels result in developmental defects and diverse human pathologies. This review discusses the crosstalk between the components of main signaling networks and the miRNA machinery, which plays a role in the context of stem cells development and provides a set of examples to illustrate the extensive relevance of potential novel therapeutic targets.

Impaired redox environment modulates cardiogenic and ion-channel gene expression in cardiac-resident and non-resident mesenchymal stem cells

Redox homeostasis plays a crucial role in the regulation of self-renewal and differentiation of stem cells. However, the behavioral actions of mesenchymal stem cells in redox imbalance state remain elusive. In the present study, the effect of redox imbalance that was induced by either hydrogen peroxide (H₂O₂) or ascorbic acid on human cardiac-resident (hC-MSCs) and non-resident (umbilical cord) mesenchymal stem cells (hUC-MSCs) was evaluated. Both cells were sensitive and responsive when exposed to either H₂O₂ or ascorbic acid at a concentration of 400 µmol/L. Ascorbic acid pre-treated cells remarkably ameliorated the reactive oxygen species level when treated with H₂O₂. The endogenous antioxidative enzyme gene (Sod1, Sod2, TRXR1 and Gpx1) expressions were escalated in both MSCs in response to reactive oxygen species elevation. In contrast, ascorbic acid pre-treated hUC-MSCs attenuated considerable anti-oxidative gene (TRXR1 and Gpx1) expressions, but not the hC-MSCs. Similarly, the cardiogenic gene (Nkx 2.5, Gata4, Mlc2a and β-MHC) and ion-channel gene ( I_KDR, I_KCa, I_to and I_Na.TTX) expressions were significantly increased in both MSCs on the oxidative state. On the contrary, reduced environment could not alter the ion-channel gene expression and negatively regulated the cardiogenic gene expressions except for troponin-1 in both cells. In conclusion, redox imbalance potently alters the cardiac-resident and non-resident MSCs stemness, cardiogenic, and ion-channel gene expressions. In comparison with cardiac-resident MSC, non-resident umbilical cord-MSC has great potential to tolerate the redox imbalance and positively respond to cardiac regeneration. Impact statement Human mesenchymal stem cells (h-MSCs) are highly promising candidates for tissue repair in cardiovascular diseases. However, the retention of cells in the infarcted area has been a major challenge due to its poor viability and/or low survival rate after transplantation. The regenerative potential of mesenchymal stem cells (MSCs) repudiate and enter into premature senescence via oxidative stress. Thus, various strategies have been attempted to improve the MSC survival in 'toxic' conditions. Similarly, we investigated the response of cardiac resident MSC (hC-MSCs) and non-resident MSCs against the oxidative stress induced by H₂O₂. Supplementation of ascorbic acid (AA) into MSCs culture profoundly rescued the stem cells from oxidative stress induced by H₂O₂. Our data showed that the pre-treatment of AA is able to inhibit the cell death and thus preserving the viability and differentiation potential of MSCs.

Stem cell therapies for congenital heart disease

Congenital heart disease (CHD) is the most prevalent congenital anomaly in newborn babies. Cardiac malformations have been induced in different animal model experiments, by perturbing some molecules that take part in the developmental pathways associated with myocyte differentiation, specification, or cardiac morphogenesis. The exact epigenetic, environmental, or genetic, basis for these molecules perturbations is yet to be understood. But, scientist have bridged this gap by introducing autologous stem cell into the defective hearts to treat CHD. The choice of stem cells to use has also raised an issue. In this review, we explore different stem cells that have been recently used, as an update into the pool of this knowledge and we suggested the future perspective into the choice of stem cells to control this disease. We propose that isolating mesenchymal stem cells from neonate will give a robust heart regeneration as compared to adults. This source are easily isolated. To unveil stem cell therapy beyond its possibility and safety, further study is required, including largescale randomized, and clinical trials to certify the efficacy of stem cell therapy.

Progenitor Hematopoietic Cells Implantation Improves Functional Capacity of End Stage Coronary Artery Disease Patients with Advanced Heart Failure

Background. Proangiogenic Hematopoietic Cells (PHC) which comprise diverse mixture of cell types are able to secrete proangiogenic factors and interesting candidate for cell therapy. The aim of this study was to seek for benefit in implantation of PHC on functional improvement in end stage coronary artery disease patients with advanced heart failure. Methods. Patients with symptomatic heart failure despite guideline directed medical therapy and LVEF less than 35% were included. Peripheral blood mononuclear cells were isolated, cultivated for 5 days, and then harvested. Flow cytometry and cell surface markers were used to characterize PHC. The PHC were delivered retrogradely via sinus coronarius. Echocardiography, myocardial perfusion, and clinical and functional data were analyzed up to 1-year observation. Results. Of 30 patients (56.4 ± 7.40 yo) preimplant NT proBNP level is 5124.5 ± 4682.50 pmol/L. Harvested cells characterized with CD133, CD34, CD45, and KDR showed 0.87 ± 0.41, 0.63 ± 0.66, 99.00 ± 2.60, and 3.22 ± 3.79%, respectively. LVEF was improved (22 ± 5.68 versus 26.8 ± 7.93, p < 0.001) during short and long term observation. Myocardial perfusion significantly improved 6 months after treatment. NYHA Class and six-minute walk test are improved during short term and long term follow-up. Conclusion. Expanded peripheral blood PHC implantation using retrograde delivery approach improved LV systolic function, myocardial perfusion, and functional capacity.

Systems-based technologies in profiling the stem cell molecular framework for cardioregenerative medicine

Over the last decade, advancements in stem cell biology have yielded a variety of sources for stem cell-based cardiovascular investigation. Stem cell behavior, whether to maintain its stable state of pluripotency or to prime toward the cardiovascular lineage is governed by a set of coordinated interactions between epigenetic, transcriptional, and translational mechanisms. The science of incorporating genes (genomics), RNA (transcriptomics), proteins (proteomics), and metabolites (metabolomics) data in a specific biological sample is known as systems biology. Integrating systems biology in progression with stem cell biologics can contribute to our knowledge of mechanisms that underlie pluripotency maintenance and guarantee fidelity of cardiac lineage specification. This review provides a brief summarization of OMICS-based strategies including transcriptomics, proteomics, and metabolomics used to understand stem cell fate and to outline molecular processes involved in heart development. Additionally, current efforts in cardioregeneration based on the "one-size-fits-all" principle limit the potential of individualized therapy in regenerative medicine. Here, we summarize recent studies that introduced systems biology into cardiovascular clinical outcomes analysis, allowing for predictive assessment for disease recurrence and patient-specific therapeutic response.

Stem cell-based therapies to promote angiogenesis in ischemic cardiovascular disease

Stem cell therapy is a promising approach for the treatment of tissue ischemia associated with myocardial infarction and peripheral arterial disease. Stem and progenitor cells derived from bone marrow or from pluripotent stem cells have shown therapeutic benefit in boosting angiogenesis as well as restoring tissue function. Notably, adult stem and progenitor cells including mononuclear cells, endothelial progenitor cells, and mesenchymal stem cells have progressed into clinical trials and have shown positive benefits. In this review, we overview the major classes of stem and progenitor cells, including pluripotent stem cells, and summarize the state of the art in applying these cell types for treating myocardial infarction and peripheral arterial disease.

Chronic High-Fat Feeding Affects the Mesenchymal Cell Population Expanded From Adipose Tissue but Not Cardiac Atria

Mesenchymal stem cells offer a promising approach to the treatment of myocardial infarction and prevention of heart failure. However, in the clinic, cells will be isolated from patients who may be suffering from comorbidities such as obesity and diabetes, which are known to adversely affect progenitor cells. Here we determined the effect of a high-fat diet (HFD) on mesenchymal stem cells from cardiac and adipose tissues. Mice were fed a HFD for 4 months, after which cardiosphere-derived cells (CDCs) were cultured from atrial tissue and adipose-derived mesenchymal cells (ADMSCs) were isolated from epididymal fat depots. HFD raised body weight, fasted plasma glucose, lactate, and insulin. Ventricle and liver tissue of HFD-fed mice showed protein changes associated with an early type 2 diabetic phenotype. At early passages, more ADMSCs were obtained from HFD-fed mice than from chow-fed mice, whereas CDC number was not affected by HFD. Migratory and clonogenic capacity and release of vascular endothelial growth factor did not differ between cells from HFD- and chow-fed animals. CDCs from chow-fed and HFD-fed mice showed no differences in surface marker expression, whereas ADMSCs from HFD-fed mice contained more cells positive for CD105, DDR2, and CD45, suggesting a high component of endothelial, fibroblast, and hematopoietic cells. Both Noggin and transforming growth factor β-supplemented medium induced an early stage of differentiation in CDCs toward the cardiomyocyte phenotype. Thus, although chronic high-fat feeding increased the number of fibroblasts and hematopoietic cells within the ADMSC population, it left cardiac progenitor cells largely unaffected.

SIGNIFICANCE

Mesenchymal cells are a promising candidate cell source for restoring lost tissue and thereby preventing heart failure. In the clinic, cells are isolated from patients who may be suffering from comorbidities such as obesity and diabetes. This study examined the effect of a high-fat diet on mesenchymal cells from cardiac and adipose tissues. It was demonstrated that a high-fat diet did not affect cardiac progenitor cells but increased the number of fibroblasts and hematopoietic cells within the adipose-derived mesenchymal cell population.

Are Endothelial Progenitor Cells the Real Solution for Cardiovascular Diseases? Focus on Controversies and Perspectives

Advanced knowledge in the field of stem cell biology and their ability to provide a cue for counteracting several diseases are leading numerous researchers to focus their attention on “regenerative medicine” as possible solutions for cardiovascular diseases (CVDs). However, the lack of consistent evidence in this arena has hampered the clinical application. The same condition affects the research on endothelial progenitor cells (EPCs), creating more confusion than comprehension. In this review, this aspect is discussed with particular emphasis. In particular, we describe biology and physiology of EPCs, outline their clinical relevance as both new predictive, diagnostic, and prognostic CVD biomarkers and therapeutic agents, discuss advantages, disadvantages, and conflicting data about their use as possible solutions for vascular impairment and clinical applications, and finally underline a very crucial aspect of EPCs “characterization and definition,” which seems to be the real cause of large heterogeneity existing in literature data on this topic.

RNA-Mediated Reprogramming of Primary Adult Human Dermal Fibroblasts into c-kit(+) Cardiac Progenitor Cells

Cardiovascular disease is the leading cause of death in the United States. Heart failure is a common, costly, and potentially fatal condition that is inadequately managed by pharmaceuticals. Cardiac repair therapies are promising alternative options. A potential cardiac repair therapy involves reprogramming human fibroblasts toward an induced cardiac progenitor-like state. We developed a clinically useful and safer reprogramming method by nonintegrative delivery of a cocktail of cardiac transcription factor-encoding mRNAs into autologous human dermal fibroblasts obtained from skin biopsies. Using this method, adult and neonatal dermal fibroblasts were reprogrammed into cardiac progenitor cells (CPCs) that expressed c-kit, Isl-1, and Nkx2.5. Furthermore, these reprogrammed CPCs differentiated into cardiomyocytes (CMs) in vitro as judged by increased expression of cardiac troponin T, α-sarcomeric actinin, RyR2, and SERCA2 and displayed enhanced caffeine-sensitive calcium release. The ability to reprogram patient-derived dermal fibroblasts into c-kit(+) CPCs and differentiate them into functional CMs provides clinicians with a potential new source of CPCs for cardiac repair from a renewable source and an alternative therapy in the treatment of heart failure.

A novel cardiac muscle-derived biomaterial reduces dyskinesia and postinfarct left ventricular remodeling in a mouse model of myocardial infarction

Extracellular matrix (ECM) degradation after myocardial infarction (MI) leaves the myocardium structurally weakened and, as a result, susceptible to early infarct zone dyskinesia and left ventricular (LV) remodeling. While various cellular and biomaterial preparations have been transplanted into the infarct zone in hopes of improving post-MI LV remodeling, an allogeneic cardiac muscle-derived ECM extract has yet to be developed and tested in the setting of reperfused MI. We sought to determine the effects of injecting a novel cardiac muscle-derived ECM into the infarct zone on early dyskinesia and LV remodeling in a mouse model of MI. Cardiac muscle ECM was extracted from frozen mouse heart tissue by a protocol that enriches for basement membrane constituents. The extract was injected into the infarct zone immediately after ischemia/reperfusion injury (n = 6). Echocardiography was performed at baseline and at days 2, 7, 14, and 28 post-MI to assess 3D LV volumes and cardiac function, as compared to infarcted controls (n = 9). Early infarct zone dyskinesia was measured on day 2 post-MI using a novel metric, the dyskinesia index. End-systolic volume was significantly reduced in the ECM-treated group compared to controls by day 14. Ejection fraction and stroke volume were also significantly improved in the ECM-treated group. ECM-treated hearts showed a significant (P < 0.005) reduction in dyskinetic motion on day 2. Thus, using high-frequency ultrasound, it was shown that treatment with a cardiac-derived ECM preparation reduced early infarct zone dyskinesia and post-MI LV remodeling in a mouse model of reperfused MI.

Origin of cardiomyocytes in the adult heart

This review article discusses the mechanisms of cardiomyogenesis in the adult heart. They include the re-entry of cardiomyocytes into the cell cycle; dedifferentiation of pre-existing cardiomyocytes, which assume an immature replicating cell phenotype; transdifferentiation of hematopoietic stem cells into cardiomyocytes; and cardiomyocytes derived from activation and lineage specification of resident cardiac stem cells. The recognition of the origin of cardiomyocytes is of critical importance for the development of strategies capable of enhancing the growth response of the myocardium; in fact, cell therapy for the decompensated heart has to be based on the acquisition of this fundamental biological knowledge.

Regenerative medicine for the heart: perspectives on stem-cell therapy

SIGNIFICANCE

Despite decades of progress in cardiovascular biology and medicine, heart disease remains the leading cause of death, and there is no cure for the failing heart. Since heart failure is mostly caused by loss or dysfunction of cardiomyocytes (CMs), replacing dead or damaged CMs with new CMs might be an ideal way to reverse the disease. However, the adult heart is composed mainly of terminally differentiated CMs that have no significant self-regeneration capacity.

RECENT ADVANCES

Stem cells have tremendous regenerative potential and, thus, current cardiac regenerative research has focused on developing stem cell sources to repair damaged myocardium.

CRITICAL ISSUES

In this review, we examine the potential sources of cells that could be used for heart therapies, including embryonic stem cells and induced pluripotent stem cells, as well as alternative methods for activating the endogenous regenerative mechanisms of the heart via transdifferentiation and cell reprogramming. We also discuss the current state of knowledge of cell purification, delivery, and retention.

FUTURE DIRECTIONS

Efforts are underway to improve the current stem cell strategies and methodologies, which will accelerate the development of innovative stem-cell therapies for heart regeneration.

Conjoint propagation and differentiation of human embryonic stem cells to cardiomyocytes in a defined microcarrier spinner culture

Introduction

Myocardial infarction is accompanied by a significant loss of cardiomyocytes (CMs). Functional CMs, differentiated from human embryonic stem cells (hESCs), offer a potentially unlimited cell source for cardiac disease therapies and regenerative cardiovascular medicine. However, conventional production methods on monolayer culture surfaces cannot adequately supply the large numbers of cells required for such treatments. To this end, an integrated microcarrier (MC) bioprocessing system for hESC propagation and subsequent CM differentiation was developed.

Methods

Production of hESC-derived CMs was initially established in monolayer cultures. This control condition was compared against hESC expansion on laminin-coated MC with cationic surface charge, in a stirred serum-free defined culture. Following expansion, the hESC/MC aggregates were placed in a CM differentiation medium, using Wnt signalling modulators in four different culture conditions. This process eliminated the need for manual colony cutting. The final optimized protocol was tested in stirred spinner flasks, combining expansion and differentiation on the same MC, with only media changes during the culture process.

Results

In the propagation phase, a 15-fold expansion of viable pluripotent HES-3 was achieved, with homogeneous sized aggregates of 316 ± 11 μm. Of the four differentiation conditions, stirred spinner flask cultures (MC-Sp) provided the best controlled aggregate sizes and yielded 1.9 × 10⁶ CM/ml, as compared to 0.5 × 10⁶ CM/ml using the monolayer cultures method: a four-fold increase in CM/ml. Similar results (1.3 × 10⁶ CM/ml) were obtained with an alternative hESC H7 line. The hESC/MC-derived CM expressed cardiac-specific transcription factors, structural, ion channel genes, and exhibited cross-striations of sarcomeric proteins, thus confirming their cardiac ontogeny. Moreover, E-4031 (0.3 μM) prolonged the QT-interval duration by 40% and verapamil (3 μM) reduced it by 45%, illustrating the suitability of these CM for pharmacological assays.

Conclusions

We have demonstrated a robust and scalable microcarrier system for generating hESC-derived CM. This platform is enabled by defined microcarrier matrices and it integrates cell propagation and differentiation within a continuous process, in serum-free culture media. It can generate significant numbers of CM, which are potentially suitable for future clinical therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/scrt498) contains supplementary material, which is available to authorized users.

Effect of transplantation of bone marrow stem cells on myocardial infarction size in a rabbit model

BACKGROUND

Intravenous transplantation has been regarded as a most safe method in stem cell therapies. There is evidence showing the homing of bone marrow stem cells (BMSCs) into the injured sites, and thus these cells can be used in the treatment of acute myocardial infarction (MI). This study aimed to investigate the effect of intravenous and epicardial transplantion of BMSCs on myocardial infarction size in a rabbit model.

METHODS

A total of 60 New Zealand rabbits were randomly divided into three groups: control group, epicardium group (group I) and ear vein group (group II). The BMSCs were collected from the tibial plateau in group I and group II, cultured and labeled. In the three groups, rabbits underwent thoracotomy and ligation of the middle left anterior descending artery. The elevation of ST segment >0.2 mV lasting for 30 minutes on the lead II and III of electrocardiogram suggested successful introduction of myocardial infarction. Two weeks after myocardial infarction, rabbits in group I were treated with autogenous BMSCs at the infarct region and those in group II received intravenous transplantation of BMSCs. In the control group, rabbits were treated with PBS following thoracotomy. Four weeks after myocardial infarction, the heart was collected from all rabbits and the infarct size was calculated. The heart was cut into sections followed by HE staining and calculation of infarct size with an image system.

RESULTS

In groups I and II, the infarct size was significantly reduced after transplantation with BMSCs when compared with the control group (P<0.05). However, there was no significant difference in the infarct size between groups I and II (P>0.05).

CONCLUSION

Transplantation of BMSCs has therapeutic effect on MI. Moreover, epicardial and intravenous transplantation of BMSCs has comparable therapeutic efficacy on myocardial infarction.

Renin inhibition improves the survival of mesenchymal stromal cells in a mouse model of myocardial infarction

The aim of this study was to determine if renin inhibition is able to improve the survival of transplanted stem cells in a mouse model of myocardial infarction. Myocardial infarction was induced in FVB/NJ inbred mice (n = 23). Bone marrow-derived mouse mesenchymal stromal cells (mMSCs, 3 × 10(5)) expressing the reporter gene firefly luciferase were delivered intramyocardially (n = 12) and monitored non-invasively by bioluminescence imaging. A group of these mice (n = 6) received aliskiren (15 mg/kg/day) via an osmotic pump implanted subcutaneously. The survival of mMSCs was significantly increased in those animals that received aliskiren leading to a significant improvement in systolic function after myocardial infarction. Histological analysis revealed a significant reduction in inflammation and collagen deposition in those mice that received aliskiren compared to controls. Renin inhibition of the ischemic myocardium is able to modulate the microenvironment improving the survival and efficacy of transplanted mMSCs in a mouse model of myocardial infarction.

Cell therapy for human ischemic heart diseases: critical review and summary of the clinical experiences

A decade ago, stem or progenitor cells held the promise of tissue regeneration in human myocardium, with the expectation that these therapies could rescue ischemic myocyte damage, enhance vascular density and rebuild injured myocardium. The accumulated evidence in 2014 indicates, however, that the therapeutic success of these cells is modest and the tissue regeneration involves much more complex processes than cell-related biologics. As the quest for the ideal cell or combination of cells continues, alternative cell types, such as resident cardiac cells, adipose-derived or phenotypic modified stem or progenitor cells have also been applied, with the objective of increasing both the number and the retention of the reparative cells in the myocardium. Two main delivery routes (intracoronary and percutaneous intramyocardial) of stem cells are currently used preferably for patients with recent acute myocardial infarction or ischemic cardiomyopathy. Other delivery modes, such as surgical or intravenous via peripheral veins or coronary sinus have also been utilized with less success. Due to the difficult recruitment of patients within conceivable timeframe into cardiac regenerative trials, meta-analyses of human cardiac cell-based studies have tried to gather sufficient number of subjects to present a statistical compelling statement, reporting modest success with a mean increase of 0.9-6.1% in left ventricular global ejection fraction. Additionally, nearly half of the long-term studies reported the disappearance of the initial benefit of this treatment. Beside further extensive efforts to increase the efficacy of currently available methods, pre-clinical experiments using new techniques such as tissue engineering or exploiting paracrine effect hold promise to regenerate injured human cardiac tissue.

Angiogenesis, cardiomyocyte proliferation and anti-fibrotic effects underlie structural preservation post-infarction by intramyocardially-injected cardiospheres

OBJECTIVE

We sought to understand the cellular and tissue-level changes underlying the attenuation of adverse remodeling by cardiosphere transplantation in acute myocardial infarction (MI).

BACKGROUND

Cardiospheres (CSps) are heart-derived multicellular clusters rich in stemness and capable of multilineage differentiation. Post-MI CSp transplantation improves left ventricular (LV) function and attenuates remodeling in both small and large animal studies. However, the mechanisms of benefit have not yet been fully elucidated.

METHODS

Four groups were studied: 1) "Sham" (Wistar Kyoto rats with thoracotomy and ligature without infarction); 2) "MI" (proximal LAD ligation with peri-infarct injection of vehicle); 3) "MI+CSp" (MI with cardiospheres injected in the peri-infarct area); 4) "Small MI" (mid-LAD ligation only).

RESULTS

In vivo 1 week after CSp transplantation, LV functional improvement was associated with an increase in cardiomyocyte proliferation. By 3 weeks, microvessel formation was enhanced, while cardiomyocyte hypertrophy and regional fibrosis were attenuated. Collagen deposition was reduced, collagen degradation was enhanced, and MMPs were upregulated. The beneficial effects of CSp transplantation were not observed in the Small MI group, indicating that the effects are not solely due to CSp-induced cardioprotection. In vitro, CSp-conditioned media reduced collagen production in coculture with fibroblasts and triggered neoangiogenesis in an ex vivo aortic ring assay.

CONCLUSION

Cardiospheres enhance cardiomyocyte proliferation and angiogenesis, and attenuate hypertrophy and fibrosis, in the ischemic myocardium. These synergistic effects underlie the attenuation of adverse remodeling by cardiospheres.

Natural ECM as biomaterial for scaffold based cardiac regeneration using adult bone marrow derived stem cells

Cellular therapy using stem cells for cardiac diseases has recently gained much interest in the scientific community due to its potential in regenerating damaged and even dead tissue and thereby restoring the organ function. Stem cells from various sources and origin are being currently used for regeneration studies directly or along with differentiation inducing agents. Long term survival and minimal side effects can be attained by using autologous cells and reduced use of inducing agents. Cardiomyogenic differentiation of adult derived stem cells has been previously reported using various inducing agents but the use of a potentially harmful DNA demethylating agent 5-azacytidine (5-azaC) has been found to be critical in almost all studies. Alternate inducing factors and conditions/stimulant like physical condition including electrical stimulation, chemical inducers and biological agents have been attempted by numerous groups to induce cardiac differentiation. Biomaterials were initially used as artificial scaffold in in vitro studies and later as a delivery vehicle. Natural ECM is the ideal biological scaffold since it contains all the components of the tissue from which it was derived except for the living cells. Constructive remodeling can be performed using such natural ECM scaffolds and stem cells since, the cells can be delivered to the site of infraction and once delivered the cells adhere and are not "lost". Due to the niche like conditions of ECM, stem cells tend to differentiate into tissue specific cells and attain several characteristics similar to that of functional cells even in absence of any directed differentiation using external inducers. The development of niche mimicking biomaterials and hybrid biomaterial can further advance directed differentiation without specific induction. The mechanical and electrical integration of these materials to the functional tissue is a problem to be addressed. The search for the perfect extracellular matrix for therapeutic applications including engineering cardiac tissue structures for post ischemic cardiac tissue regeneration continues.

The pharmacology of regenerative medicine

Regenerative medicine is a rapidly evolving multidisciplinary, translational research enterprise whose explicit purpose is to advance technologies for the repair and replacement of damaged cells, tissues, and organs. Scientific progress in the field has been steady and expectations for its robust clinical application continue to rise. The major thesis of this review is that the pharmacological sciences will contribute critically to the accelerated translational progress and clinical utility of regenerative medicine technologies. In 2007, we coined the phrase "regenerative pharmacology" to describe the enormous possibilities that could occur at the interface between pharmacology, regenerative medicine, and tissue engineering. The operational definition of regenerative pharmacology is "the application of pharmacological sciences to accelerate, optimize, and characterize (either in vitro or in vivo) the development, maturation, and function of bioengineered and regenerating tissues." As such, regenerative pharmacology seeks to cure disease through restoration of tissue/organ function. This strategy is distinct from standard pharmacotherapy, which is often limited to the amelioration of symptoms. Our goal here is to get pharmacologists more involved in this field of research by exposing them to the tools, opportunities, challenges, and interdisciplinary expertise that will be required to ensure awareness and galvanize involvement. To this end, we illustrate ways in which the pharmacological sciences can drive future innovations in regenerative medicine and tissue engineering and thus help to revolutionize the discovery of curative therapeutics. Hopefully, the broad foundational knowledge provided herein will spark sustained conversations among experts in diverse fields of scientific research to the benefit of all.

Noninvasive monitoring of oxidative stress in transplanted mesenchymal stromal cells

OBJECTIVES

The goal of this study was to validate a pathway-specific reporter gene that could be used to noninvasively image the oxidative status of progenitor cells.

BACKGROUND

In cell therapy studies, reporter gene imaging plays a valuable role in the assessment of cell fate in living subjects. After myocardial injury, noxious stimuli in the host tissue confer oxidative stress to transplanted cells that may influence their survival and reparative function.

METHODS

Rat mesenchymal stromal cells (MSCs) were studied for phenotypic evidence of increased oxidative stress under in vitro stress. On the basis of their up-regulation of the pro-oxidant enzyme p67(phox) subunit of nicotinamide adenine dinucleotide phosphate (NAD[P]H oxidase p67(phox)), an oxidative stress sensor was constructed, comprising the firefly luciferase (Fluc) reporter gene driven by the NAD(P)H p67(phox) promoter. MSCs cotransfected with NAD(P)H p67(phox)-Fluc and a cell viability reporter gene (cytomegalovirus-Renilla luciferase) were studied under in vitro and in vivo pro-oxidant conditions.

RESULTS

After in vitro validation of the sensor during low-serum culture, transfected MSCs were transplanted into a rat model of myocardial ischemia/reperfusion (IR) and monitored by using bioluminescence imaging. Compared with sham controls (no IR), cardiac Fluc intensity was significantly higher in IR rats (3.5-fold at 6 h, 2.6-fold at 24 h, 5.4-fold at 48 h; p < 0.01), indicating increased cellular oxidative stress. This finding was corroborated by ex vivo luminometry after correcting for Renilla luciferase activity as a measure of viable MSC number (Fluc:Renilla luciferase ratio 0.011 ± 0.003 for sham vs. 0.026 ± 0.004 for IR at 48 h; p < 0.05). Furthermore, in IR animals that received MSCs preconditioned with an antioxidant agent (tempol), Fluc signal was strongly attenuated, substantiating the specificity of the oxidative stress sensor.

CONCLUSIONS

Pathway-specific reporter gene imaging allows assessment of changes in the oxidative status of MSCs after delivery to ischemic myocardium, providing a template to monitor key biological interactions between transplanted cells and their host environment in living subjects.

Regenerative medicine primer

The pandemic of chronic diseases, compounded by the scarcity of usable donor organs, mandates radical innovation to address the growing unmet needs of individuals and populations. Beyond life-extending measures that are often the last available option, regenerative strategies offer transformative solutions in treating degenerative conditions. By leveraging newfound knowledge of the intimate processes fundamental to organogenesis and healing, the emerging regenerative armamentarium aims to boost the aptitude of human tissues for self-renewal. Regenerative technologies strive to promote, augment, and reestablish native repair processes, restituting organ structure and function. Multimodal regenerative approaches incorporate transplant of healthy tissues into damaged environments, prompt the body to enact a regenerative response in damaged tissues, and use tissue engineering to manufacture new tissue. Stem cells and their products have a unique aptitude to form specialized tissues and promote repair signaling, providing active ingredients of regenerative regimens. Concomitantly, advances in materials science and biotechnology have unlocked additional prospects for growing tissue grafts and engineering organs. Translation of regenerative principles into practice is feasible and safe in the clinical setting. Regenerative medicine and surgery are, thus, poised to transit from proof-of-principle studies toward clinical validation and, ultimately, standardization, paving the way for next-generation individualized management algorithms.

Cardiopoietic stem cell therapy in heart failure: the C-CURE (Cardiopoietic stem Cell therapy in heart failURE) multicenter randomized trial with lineage-specified biologics

OBJECTIVES

This study sought to evaluate the feasibility and safety of autologous bone marrow-derived and cardiogenically oriented mesenchymal stem cell therapy and to probe for signs of efficacy in patients with chronic heart failure.

BACKGROUND

In pre-clinical heart failure models, cardiopoietic stem cell therapy improves left ventricular function and blunts pathological remodeling.

METHODS

The C-CURE (Cardiopoietic stem Cell therapy in heart failURE) trial, a prospective, multicenter, randomized trial, was conducted in patients with heart failure of ischemic origin who received standard of care or standard of care plus lineage-specified stem cells. In the cell therapy arm, bone marrow was harvested and isolated mesenchymal stem cells were exposed to a cardiogenic cocktail. Derived cardiopoietic stem cells, meeting release criteria under Good Manufacturing Practice, were delivered by endomyocardial injections guided by left ventricular electromechanical mapping. Data acquisition and analysis were performed in blinded fashion. The primary endpoint was feasibility/safety at 2-year follow-up. Secondary endpoints included cardiac structure/function and measures of global clinical performance 6 months post-therapy.

RESULTS

Mesenchymal stem cell cocktail-based priming was achieved for each patient with the dose attained in 75% and delivery without complications in 100% of cases. There was no evidence of increased cardiac or systemic toxicity induced by cardiopoietic cell therapy. Left ventricular ejection fraction was improved by cell therapy (from 27.5 ± 1.0% to 34.5 ± 1.1%) versus standard of care alone (from 27.8 ± 2.0% to 28.0 ± 1.8%, p < 0.0001) and was associated with a reduction in left ventricular end-systolic volume (-24.8 ± 3.0 ml vs. -8.8 ± 3.9 ml, p < 0.001). Cell therapy also improved the 6-min walk distance (+62 ± 18 m vs. -15 ± 20 m, p < 0.01) and provided a superior composite clinical score encompassing cardiac parameters in tandem with New York Heart Association functional class, quality of life, physical performance, hospitalization, and event-free survival.

CONCLUSIONS

The C-CURE trial implements the paradigm of lineage guidance in cell therapy. Cardiopoietic stem cell therapy was found feasible and safe with signs of benefit in chronic heart failure, meriting definitive clinical evaluation. (C-Cure Clinical Trial; NCT00810238).

Allogeneic cardiospheres safely boost cardiac function and attenuate adverse remodeling after myocardial infarction in immunologically mismatched rat strains

OBJECTIVES

We sought to characterize the immunologic profile of allogeneic cardiospheres, which are 3-dimensional, self-assembling, cardiac-derived microtissues, and to evaluate their safety and efficacy in repairing ischemic heart tissue.

BACKGROUND

Intramyocardial injection of autologous cardiospheres ameliorates remodeling and improves global function in infarcted myocardium. It is as yet unknown whether allogeneic cardiospheres are similarly effective without eliciting deleterious immune reactions.

METHODS

We expanded cardiospheres from male Wistar Kyoto rat hearts and injected them surgically in the peri-infarct zone of Wistar Kyoto (syngeneic group, n = 28) and Brown Norway female rats (allogeneic group, n = 29). Female rats from both strains (n = 37) injected with normal saline served as controls.

RESULTS

In vitro, cardiospheres expressed a low immunogenic profile and inhibited proliferation of alloreactive T cells. In vivo, cell engraftment was similar in the syngeneic and allogeneic groups 1 week and 3 weeks after transplantation. Reductions in scar size and scar collagen content and increases in viable mass in the risk region were accompanied by improvements in left ventricular function and attenuation of left ventricle remodeling that were sustained during 6 months of follow up. Transplantation of allogeneic cardiospheres increased tissue expression of the regenerative growth factors vascular endothelial growth factor, hepatocyte growth factor, and insulin-like growth factor-1, stimulating angiogenesis. Syngeneic and allogeneic cardiospheres attenuated the inflammatory response observed histologically in the peri-infarct region.

CONCLUSIONS

Allogeneic cardiospheres increase viable myocardium, decrease scar, improve function, and attenuate adverse remodeling in the infarcted rat heart, without deleterious immunological sequelae. These observations lay the groundwork for developing cardiospheres as a novel off-the-shelf microtissue product for myocardial regeneration.

Current status and perspectives on stem cell-based therapies undergoing clinical trials for regenerative medicine: case studies

BACKGROUND

Apart from haematopoietic stem cell transplantation for haematological disorders many stem cell-based therapies are experimental. However, with only 12 years between human embryonic stem cell isolation and the first clinical trial, development of stem cell products for regenerative medicine has been rapid and numerous clinical trials have begun to investigate their therapeutic potential.

SOURCE OF DATA

This review summarizes key clinical trial data, current and future perspectives on stem cell-based products undergoing clinical trials, based on literature search and author research.

AREAS OF AGREEMENT

It is widely recognized that the ability to stimulate stem cell differentiation into specialized cells for use as cellular therapies will revolutionize health care and offer major hope for numerous diseases for which there are limited or no therapeutic options.

AREAS OF CONTROVERSY

Stem cell-based products are unique and cover a large range of disorders to be treated; therefore, there is significant potential for variation in cell source, type, processing manipulation, the bioprocessing approach and scalability, the cost and purity of manufacture, final product quality and mode of action. As such there are gaps in regulatory and manufacturing frameworks and technologies, only a small number of products are currently within late phase clinical trials and few products have achieved commercialization.

GROWING POINTS

Recent developments are encouraging acceleration through the difficulties encountered en route to clinical trials and commercialization of stem cell therapies.

AREAS TIMELY FOR DEVELOPING RESEARCH

The field is growing year on year with the first clinical trial using induced pluripotent stem cells anticipated by end 2013.

Meeting the need for regenerative therapies: translation-focused analysis of U.S. regenerative medicine opportunities in cardiovascular and peripheral vascular medicine using detailed incidence data

Cardiac and vascular diseases represent one of the most substantial medical areas for the applications of regenerative medicine. Despite advances in endovascular repair, surgical intervention, and disease management, atherosclerosis and heart failure continue to be prominent health problems. This report analyzes the regenerative medicine treatment opportunities in both cardiovascular and peripheral vascular repair, examining the treatment opportunities for tissue-engineered vascular grafts as well as cell-based therapies. U.S. hospital discharge data were used to generate a detailed estimate of the relative target populations for cardiac and vascular disease. Gap analyses were performed for vascular access, small caliber vascular grafts, and cell-based therapies for revascularization and heart failure. The analysis compared current alternatives, gaps in medical need, and what a tissue-engineered or regenerative alternative should achieve for optimum medical and commercial feasibility. Although the number of coronary bypass grafts vastly outnumbered peripheral grafts, a detailed consideration of re-grafts and the success of first grafts combined with gap analysis (GAP) leads us to conclude that peripheral vascular disease is the more commercially feasible and attractive target opportunity for engineered small caliber grafts for the foreseeable future. Cardiac bypass would need substantial long-term clinical experience, which could be a significant hurdle. Vascular access, often regarded as a first-in-man indication, is an excellent opportunity for an engineered graft as an alternative to arteriovenous fistula that could overcome complications associated with a prosthetic graft. The GAP also suggests that for heart failure, cellular therapies should link near-term changes in repair, such as improvement in cardiac output and reduced scarring with limiting progression of the disease, reducing the need for complex pharmacologic management, and reducing rates of hospitalization. Naturally, researchers must determine where their technology and know-how can be applied most effectively, but it is clear from our analysis that an astute strategy in the use of science and technology will be important to successful translation in this space.

Reawakening atlas: chemical approaches to repair or replace dysfunctional musculature

Muscle diseases are major health concerns. For example, ischemic heart disease is the third most common cause of death. Cell therapy is an attractive approach for treating muscle diseases, although this is hampered by the need to generate large numbers of functional muscle cells. Small molecules have become established as attractive tools for modulating cell behavior and, in this review, we discuss the recent, rapid research advances made in the development of small molecule methods to facilitate the production of functional cardiac, skeletal, and smooth muscle cells. We also describe how new developments in small molecule strategies for muscle disease aim to induce repair and remodelling of the damaged tissues in situ. Recent progress has been made in developing small molecule cocktails that induce skeletal muscle regeneration, and these are discussed in a broader context, because a similar phenomenon occurs in the early stages of salamander appendage regeneration. Although formidable technical hurdles still remain, these new advances in small molecule-based methodologies should provide hope that cell therapies for patients suffering from muscle disease can be developed in the near future.

Intramyocardial injection of bone marrow mononuclear cells in chronic myocardial ischemia patients after previous placebo injection improves myocardial perfusion and anginal symptoms: an intra-patient comparison

BACKGROUND

We recently demonstrated in a randomized, double-blind, placebo-controlled trial that intramyocardial bone marrow cell (BMC) injection is associated with improvements in myocardial perfusion and anginal symptoms in chronic myocardial ischemia patients. In the present study the results of the crossover phase of this trial, in which patients previously treated with placebo received autologous BMC injections are reported. This allows a unique intra-patient comparison on the effect of BMC versus placebo injection with elimination of patient-related confounding factors.

METHODS

In 16 patients (14 male, 64 ± 10 years), who previously received intramyocardial placebo injections in the setting of a randomized trial, 100 × 10(6) BMC were injected using the NOGA-system. Canadian Cardiovascular Society angina score and quality of life were evaluated at baseline, 3 and 6 months. Tc-99m single photon emission computed tomography and magnetic resonance imaging were performed at baseline and 3 months to assess myocardial perfusion and left ventricular (LV) function.

RESULTS

Canadian Cardiovascular Society score and quality of life improved significantly after BMC injection as compared to placebo (P = 0.01 and P = 0.02, respectively). Single photon emission computed tomography revealed a significant greater improvement (P = 0.03) in summed stress score after BMC injection as compared to placebo. LV end-systolic volume significantly decreased after BMC injection but not after placebo injection. LV end-diastolic volume and LV ejection fraction did not change.

CONCLUSION

Intramyocardial BMC injection in patients with chronic myocardial ischemia who previously received intramyocardial placebo treatment resulted in significant improvement in angina symptoms and myocardial perfusion. These results confirm the outcome of our previously reported randomized trial.

Human umbilical cord perivascular cells exhibit enhanced cardiomyocyte reprogramming and cardiac function after experimental acute myocardial infarction

We were interested in evaluating the ability of the mesenchymal stromal cell (MSC) population, human umbilical cord perivascular cells (HUCPVCs), to undergo cardiomyocyte reprogramming in an established coculture system with rat embryonic cardiomyocytes. Results were compared with human bone marrow-derived (BM) MSCs. The transcription factors GATA4 and Mef 2c were expressed in HUCPVCs but not BM-MSCs at baseline and, at 7 days, increased 7.6- and 3.5-fold, respectively, compared with BM-MSCs. Although cardiac-specific gene expression increased in both cell types in coculture, upregulation was more significant in HUCPVCs, consistent with Mef 2c-GATA4 synergism. Using a lentivector with eGFP transcribed from the α-myosin heavy chain (α-MHC) promoter, we found that cardiac gene expression was greater in HUCPVCs than BM-MSCs after 14 days coculture (52±17% vs. 29±6%, respectively). A higher frequency of HUCPVCs expressed α-MHC protein compared with BM-MSCs (11.6±0.9% vs. 5.3±0.3%); however, both cell types retained MSC-associated determinants. We also assessed the ability of the MSC types to mediate cardiac regeneration in a NOD/SCID γ mouse model of acute myocardial infarction (AMI). Fourteen days after AMI, cardiac function was significantly better in cell-treated mice compared with control animals and HUCPVCs exhibited greater improvement. Although human cells persisted in the infarct area, the frequency of α-MHC expression was low. Our results indicate that HUCPVCs exhibit a greater degree of cardiomyocyte reprogramming but that differentiation for both cell types is partial. We conclude that HUCPVCs may be preferable to BM-MSCs in the cell therapy of AMI.

Stem cell-based therapy for ischemic heart disease

Despite great advances in therapy over the past decades, ischemic heart disease (IHD) remains the leading cause of death worldwide because the decrease in mortality after acute myocardial infarction (AMI) leads to a longer life span in patients with chronic postinfarct heart failure (HF). There are no existing medical treatments that can cure chronic HF and the only currently available therapeutic option for end-stage HF is heart transplantation. However, transplantation is limited by the shortage of donor organs and patients require lifelong immunosuppression. In the past 10 years, stem cell-based cardiac therapy has been proposed as a promising approach for the treatment of IHD. There is a variety of potential stem cell types for cardiac repair and regeneration, including bone marrow cells (BMCs), resident cardiac stem cells (CSCs) and induced pluripotent stem cells (iPSCs). Stem cell-based therapy may comprise cell transplantation or cardiac tissue engineering (CTE), which might be an attractive alternative to solve the problems of low retention and poor survival of transplanted cells. This review focuses on the characteristics of stem cells from various sources and discusses the strategies of stem cell-based therapy for the treatment of IHD.

[Cell therapy for ischemic heart disease]

Ischemic heart disease is the leading cause of death and heart failure worldwide. That is why it is important to develop new therapeutic modalities to decrease mortality and long-term complications in these patients. One of the main lines of research worldwide is myocardial regeneration, using progenitor cells in order to improve systolic and diastolic function in patients with ischemic heart disease, as well as to increase their survival. There have been carried out, with great enthusiasm worldwide, human and animal studies to define the usefulness of stem cells in the management of patients with ischemic heart disease. Today, regenerative therapy in ischemic heart disease is considered a novel therapeutic tool, with substantial theoretical benefits and few side effects. Here we present the scientific principles that support the use of this therapy, discuss the current clinical evidence available; and point out the controversial issues still not clarified on its use and usefulness in the short and long term.

Human mesenchymal stem cells: from immunophenotyping by flow cytometry to clinical applications

Modern medicine will unequivocally include regenerative medicine as a major breakthrough in the re-establishment of damaged or lost tissues due to degenerative diseases or injury. In this scenario, millions of patients worldwide can have their quality of life improved by stem cell implantation coupled with endogenous secretion or administration of survival and differentiation promoting factors. Large efforts, relying mostly on flow cytometry and imaging techniques, have been put into cell isolation, immunophenotyping, and studies of differentiation properties of stem cells of diverse origins. Mesenchymal stem cells (MSCs) are particularly relevant for therapy due to their simplicity of isolation. A minimal phenotypic pattern for the identification of MSCs cells requires them to be immunopositive for CD73, CD90, and CD105 expression, while being negative for CD34, CD45, and HLA-DR and other surface markers. MSCs identified by their cell surface marker expression pattern can be readily purified from patient's bone marrow and adipose tissues. Following expansion and/or predifferentiation into a desired tissue type, stem cells can be reimplanted for tissue repair in the same patient, virtually eliminating rejection problems. Transplantation of MSCs is subject of almost 200 clinical trials to cure and treat a very broad range of conditions, including bone, heart, and neurodegenerative diseases. Immediate or medium term improvements of clinical symptoms have been reported as results of many clinical studies.

Myocardial cell sheet therapy and cardiac function

Heart failure (HF) is the leading cause of death in developed countries. Regenerative medicine has the potential to drastically improve treatment for advanced HF. Stem cell-based medicine has received attention as a promising candidate therapy over the past decade; however, it has not yet realized this potential in terms of reliability. The cell sheet is an innovative technology for constructing aligned graft cells, and several cell sources have been investigated for making a feasible cell sheet. The most representative thus far is skeletal myoblast, although such cells raise the issue of arrhythmogenicity. Regenerative cardiomyocytes (CMs) derived from pluripotent stem cells (PSCs), such as embryonic stem cells or induced PSCs, are the most promising, because a myocardial cell sheet (MCS) constructed with regenerative CMs can potentially enable contraction recovery and electromechanical coupling with host CMs. The functional outcomes of experimental MCS are reduction of ventricular wall stress and paracrine effects rather than contraction recovery. Several technical obstacles still hamper the clinical application of MCSs, with graft survival the most pivotal issue. Ischemia, apoptosis, inflammation, and immune response can all cause graft cell death, and a stable blood supply to the MCS is critical for successful engraftment. Ventricular tachycardia must also be considered in any myocardial cell therapy, and multiple layering of MCS (>3 layers) is necessary to reconstruct human myocardium. Innervation is also a potential issue. The future application of myocardial cell therapy with MCS for advanced HF depends on resolving these difficulties.